Apply the Carer Support Payment earnings limit

changelog.d/2345.fixed.md

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+- Applied the Carer Support Payment earnings limit, including its own dated thresholds and favorable fractional-penny rule.

changelog.d/2473-main-ni-reader.fixed.md

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+Preserve age-conditioned National Insurance deductions when validating Carer Support Payment earnings after main integration.

docs/book/assumptions/carer-support-payment-earnings.md

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+# Carer Support Payment earnings
+
+Carer Support Payment (CSP) has an earnings limit. Regulation 14 of the
+[Carer's Assistance Regulations 2023](https://www.legislation.gov.uk/ssi/2023/302/regulation/14)
+excludes a carer when the earnings counted for the relevant award week exceed
+the limit. A reported Carer's Allowance award does not exempt them.
+
+## Limits and penny fractions
+
+CSP has its own Sunday effective dates, separate from Carer's Allowance:
+
+| Effective date | Weekly limit |
+| --- | ---: |
+| 19 November 2023 | £139 |
+| 7 April 2024 | £151 |
+| 6 April 2025 | £196 |
+| 5 April 2026 | £204 |
+
+The limit is inclusive. [Schedule 2 paragraph 4](https://www.legislation.gov.uk/ssi/2023/302/schedule/2/paragraph/4)
+handles a fractional penny in the individual's favour. At the final earnings
+test, £204.005 a week counts as £204.00 and passes; £204.01 exceeds the £204
+limit. The model compares annual earnings with the first excluded weekly
+penny amount multiplied by 52, in the earnings array's numeric precision.
+This applies the penny rule without an extra tolerance or rounding annual
+earnings before converting them to a weekly amount.
+
+## Annual earnings approximation
+
+The model reuses `carers_allowance_earnings`, a Person-level annual amount in
+pounds. It deducts modelled employment tax and primary Class 1 contributions,
+notional tax and contributions on self-employment profits, and half the
+individual's pension contributions. Partner and cared-for-person earnings do
+not enter the carer's test. Employer pension contributions are not deducted.
+
+Annual net earnings are spread evenly over 52 weeks. Constant-through-year
+inputs match the weekly comparison; varying earnings may not. Originally,
+regulation 14 assessed that award week's earnings. From 16 November 2025 it
+assesses the immediately preceding award week. Annual inputs cannot distinguish
+those weeks or reproduce all pay-period and averaging cases in schedule 2.
+
+The shared reader approximates employment tax using PAYE on pay alone with a
+standard code, rather than actual withholding. It does not represent all
+statutory care-charge deductions and disregards. Reusing it does not certify
+that every schedule 2 calculation is implemented.
+
+## Coverage and other conditions
+
+Raw parameter dates retain the statutory dates above. The existing annual
+parameter conversion samples 30 April for a named fiscal year; the model's
+2026 value therefore represents the £204 limit, rather than a claim that it
+legally began on 1 January. CSP remains modelled from 2025, with the previous
+Carer's Allowance route retained for Scotland in earlier model years. This
+change does not extend coverage back to the 2023 pilot.
+
+The existing caring-hours, reported-receipt and take-up conditions remain.
+Age, education, the cared-for person's qualifying-benefit conditions and the
+full claim-status rules are separate gaps. Earnings above the limit remove
+underlying CSP entitlement before the overlapping-benefit calculation. This
+differs from an overlapping benefit reducing an otherwise entitled person's
+payment to zero. The Scottish Carer Supplement is paid only when CSP is
+payable. Caring hours and reported caring can still qualify a person for the
+Universal Credit carer element, which does not apply this earnings limit.
+
+## Integration dependencies
+
+The shared Carer’s Allowance earnings reader retains the age-conditioned Class 2
+and Class 4 deductions from merged [PR #2444](https://github.com/PolicyEngine/policyengine-uk/pull/2444).
+Natural trading-income cases cover exemption after State Pension age and Class 4
+liability in the tax year that pensionable age is reached. The existing annual
+approximation remains. [PR #2474](https://github.com/PolicyEngine/policyengine-uk/pull/2474)
+is the separate minimum-age change and must retain this earnings condition when
+stacked or integrated.
+
+The open [PR #2518](https://github.com/PolicyEngine/policyengine-uk/pull/2518)
+changes a shared Carer’s Allowance earnings parameter. Once this reader is shared
+with CSP, that parameter’s effects on CSP require coordination and validation;
+this page does not assume the two benefits remain independent of that parameter.

policyengine_uk/parameters/gov/social_security_scotland/carer_support_payment/earnings_limit.yaml

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+description: Weekly net earnings limit for Carer Support Payment, after the favorable fractional-penny rule.
+metadata:
+  economy: false
+  period: week
+  unit: currency-GBP
+  label: Carer Support Payment earnings limit
+  reference:
+    - title: The Carer's Assistance (Carer Support Payment) (Scotland) Regulations 2023, regulation 14
+      href: https://www.legislation.gov.uk/ssi/2023/302/regulation/14
+values:
+  2023-11-19:
+    value: 139
+    reference:
+      - title: The Carer's Assistance (Carer Support Payment) (Scotland) Regulations 2023, regulations 1 and 14 as made
+        href: https://www.legislation.gov.uk/ssi/2023/302/made
+  2024-04-07:
+    value: 151
+    reference:
+      - title: Regulation 14 as amended from 7 April 2024 by SSI 2024/105, regulation 7(2)
+        href: https://www.legislation.gov.uk/ssi/2023/302/regulation/14/2024-04-07
+  2025-04-06:
+    value: 196
+    reference:
+      - title: Regulation 14 as amended from 6 April 2025 by SSI 2025/100, regulation 13(2)
+        href: https://www.legislation.gov.uk/ssi/2023/302/regulation/14/2025-04-06
+  2026-04-05:
+    value: 204
+    reference:
+      - title: The Social Security (Up-rating) (Miscellaneous Amendments) (Scotland) Regulations 2026, regulation 12(2)
+        href: https://www.legislation.gov.uk/ssi/2026/170/regulation/12/made

policyengine_uk/parameters/gov/social_security_scotland/carer_support_payment/earnings_rounding_precision.yaml

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+description: Penny precision for the favorable fractional-penny calculation of Carer Support Payment weekly earnings.
+values:
+  2023-11-19: 0.01
+metadata:
+  economy: false
+  period: week
+  unit: currency-GBP
+  label: Carer Support Payment earnings rounding precision
+  reference:
+    - title: The Carer's Assistance (Carer Support Payment) (Scotland) Regulations 2023, schedule 2 paragraph 4
+      href: https://www.legislation.gov.uk/ssi/2023/302/schedule/2/paragraph/4